Category Archives: UAVs

More Morphin Copters

Apparently, reconfiguring drones is an idea whose time has come.

Earlier I noted an admirably simple folding quad copter, from a French team.  This week I read of a group in Tokyo who see your quad copter and raise you four—a snaky octocopter that can configure in a zillion ways—the flying DRAGON [2] .  So there!

This flying snake thing has modules connected by gimbals, each with  two rotors, also on gimbals.  Altogether, the assembly can bend in 6DOF, just like a robot arm.   A flying robot arm.

The researchers conceptualize this robot as a sort of overactuated flying arm that can both form new shapes and use those shapes to interact with the world around it by manipulating objects.” (from [1])

Reconfiguring in flight is, well, complicated.

A key feature of this design is that the rotors aren’t all in the same plane as in a rigid quadcopter. This is actually a key to stability:  the rotors point in multiple directions and the body is rigid, yielding stable flight and hovering.

“To achieve an arbitrary 6DoF pose in the air, rotor disks cannot be aligned in the same plane, which is the case for traditional multirotors.” ([2], p. 1177)

The control system is modular, featuring “spinal” and “link” controllers, as well as a high level processor.  Indeed, the device looks like nothing so much as a hovering spine.

The demo video shows an impressive maneuver, slinking thorough a small horizontal hole, unfurling while hovering and slipping link by link up through the floor.  Pretty cool.

What’s more, the software autonomously determines the transformation needed. Very impressive.

This flying robot arm has the potential to be used as a flying robot arm:  it can poke and grasp and carry cargo.

It will be interesting to see how this approach compares to swarms of rigid copters.  What are the advantages and disadvantages of a handful of really complicated snakey fliers versus a constellation of many simpler fliers.   (A swarm is probably harder to shoot down.)

I predict that this will soon be a moot question, because there will be swarms that can lock together into spines, and disperse again into drones, as needed.

  1. Evan Ackerman, Flying Dragon Robot Transforms Itself to Squeeze Through Gaps, in IEEE Spectrum – Robotics. 2018.
  2. M. Zhao, T. Anzai, F. Shi, X. Chen, K. Okada, and M. Inaba, Design, Modeling, and Control of an Aerial Robot DRAGON: A Dual-Rotor-Embedded Multilink Robot With the Ability of Multi-Degree-of-Freedom Aerial Transformation. IEEE Robotics and Automation Letters, 3 (2):1176-1183, 2018.


Robot Wednesday


Mighty Morphin Copter

This is the decade of the quad copter. The basic body plan of the quad rotor has been hugely successful in uncounted variants and applications. It has become nearly synonymous with UAV and “drones” for most people.

While there are thousands of versions of this type of flyer available, most of them are rigid and unchangeable during flight.

A group of researchers in France report this summer on a “morphing” quad copter, capable of rapidly reconfiguring in mid flight [1]. In particular, the copter reconfigures to fly through a restricted area, i.e., it folds up to be skinnier.


The trick, of course, is to keep flying even as the structure of the aircraft changes rather significantly.  Quad copters are controlled by the different lift of the props, which means that shifting the position of the rotors is dramatically changing the control of the craft.  In this case, the rotors are morphed from a rectangle to a linear array.

The control software must adjust to the change, taking account of the geometry of the rotors to maintain control and trajectory of the craft.  In the folded formation, there is much less control over roll, so flight is less stable.  But the system works well enough to fly through a constrained aperture at speed, folding to about half width and back again.


  1. Valentin Riviere, Augustin Manecy, and Stephane Viollet, Agile Robotic Fliers: A Morphing-Based Approach. Soft Robotics, 2018.


Robot Wednesday

Interplanetary Copters!

The last decade has seen an incredible bloom in small autonomous and remote controlled helicopters, AKA drones. It isn’t far wrong to call them ubiquitous, and probably the characteristic technology of the 2010s. (Sorry Siri.)

It isn’t surprising, then that NASA (the National Aeronautics and Space Admin.) has some ideas about what to do with robot helicopters.

This month it is confirmed that the next planned Mars rover will have a copter aboard [3].  (To date, this appears to be known as “The Mars Helicopter”, but surely it will need to be christened with some catchy moniker. “The Red Planet Baron”?  “The Martian Air Patrol”? “The Red Planet Express”?)

This won’t be a garden variety quad copter.  Mars in not Earth, and, in particular, Mars “air” is not Earth air. The atmosphere is thin, real thin, which means less lift.  On the other hand, gravity is less than on Earth. The design will feature larger rotors spinning much faster than Terra copters.

Operating on Mars will have to be autonomous, and the flying conditions could be really hairy. Martian air is not only thin, it is cold and dusty.  And the terrain is unknown.  The odds of operating without mishap are small. The first unexpected sand storm, and it may be curtains for the flyer.  Mean time to failure may be hours or less.

Limits of power and radios means that the first mission will be short range. Unfortunately, a 2 kilo UAV will probably only do visual inspections of the surface, albeit with an option for tight close ups.  Still it will extend the footprint of the rover by quite a bit, and potentially enable atmospheric sampling.

This isn’t the only extraterrestrial copter in the works.  If Mars has a cold, thin atmosphere, Saturn’s moon Titan may have methane lakes and weather, and possibly an ocean under the icy surface.   Titan also has a cold thick atmosphere, and really low gravity—favorable for helicopters!

Planning for a landing on this intriguing world is looking at a copter, called “Dragonfly” [1, 2]. The Dragonfly design is a bit larger, and is an octocopter. <<link>>  (It is noted that it should be able to continue to operate even if one or more rotors break.)  Dragonfly is also contemplated to have a nuclear power source—Titan is too far away for solar power to be a useful option.

Titan is a lot farther away than Mars, and communications will be difficult due to radiation and other interference.  The Dragonfly will have to be really, really autonomous.

Flying conditions on Titan are unknown, but theoretically could include clouds, rain, snow, storms, who knows.  The air is methane and hydrocarbons which could gum up the flyer. Honestly, mean time to failure could be zero—it may not be able to even take off.

Both these copters are significantly different from what you might buy at the hobby store or build in your local makerspace.  But prototypes can be flown on Earth, and the autonomous control algorithms are actually not that different from Earth bound UAVs. This is a good thing, because we have to program them here, before we actually send them off.

In fact, I think this is one of the advantages of small helicopters for this use. Flying is flying, once you adjust for pressure, density, etc. It’s probably not as tricky as driving on unknown terrain.  We should be able to design autonomous software that works OK on Mars and Titan.  (Says Bob, who doesn’t have to actually make it work.)

Finally, I’ll note that a mission to Titan should ideally include an autonomous submarine or better, a tunneling submarine, to explore the lakes and cracks. I’m sure this is under study, but I don’t know that it will be possible on the first landing.

  1. Evan Ackerman, How to Conquer Titan With a Nuclear Quad Octocopter, in IEEE Spectrum – Automation. 2017.
  2. Dragonfly. Dragonfly Titan Rotorcraft Lander. 2017,
  3. Karen Northon, Mars Helicopter to Fly on NASA’s Next Red Planet Rover Mission, in NASA News Releases. 2018.


We must go to Titan! We must go to Europa!

Ice Worlds, Ho!

Robot Wednesday

Robot Concepts: Legs Plus Lift

Lunacity seems to be lunacy, or at least fantasy. “Personal jetpacks” are at the edge of possibility, requiring impractically huge amounts of power to lift a person (and, once lifted, are impossible to control).  But that doesn’t mean that moderate sized personal jetpacks have no possible use.

Two recent projects illustrate how copter tech can be combined with articulated bodies to create interesting hybrid robots.

One interesting concept is to add ducted fans to the feet of a bipedal (or any number of pedal) robot.  The lift is used to aid the robot when it needs to stretch for a long step over a gap.  The video makes this idea pretty clear:  one foot is anchored, and the other uses the thrust to keep balanced while stepping over the void.

This is the “Lunacity” idea applied to each foot independently, and it is plausible (if noisy and annoying).  There isn’t much hope of lifting the whole robot, but the thrusters probably can add useful “weightlessness” to parts of the robot.  In this case, the feet, but the same idea might add lifting power to arms or sensor stalks.

A second project sort of goes the other way;  adding a light weigh, foldable “origami” arm to a flying UAV [2].   The idea is to have a compact arm that extends the capabilities of the flyer, within the weight and space limits of a small aircraft.  The design unfolds and folds with only a single motor.  Origami is so cool!

Instead of adding lifters to the robot, the robot arm is added to the flyer, to make a hybrid flying grasper.  I think there is no reason why there couldn’t be two arms, or the arms can’t be legs, or some other combination.

I look forward to even more creative hybridization, combining controllable rigid structures with lifting bodies in transformer-like multimode robots.

  1. Evan Ackerman, Bipedal Robot Uses Jet-Powered Feet to Step Over Large Gaps, in IEEE Spectrum – robotis. 2018.
  2. Suk-Jun Kim, Dae-Young Lee, Gwang-Pil Jung, and Kyu-Jin Cho, An origami-inspired, self-locking robotic arm that can be folded flat. Science Robotics, 3 (16) 2018.


Robot Wednesday


Drones Counting Ducks Down Under

One of the oldest citizen science projects is bird watching.  For more than a century, enthusiastic birders have amassed vast datasets of avian sightings.  To date, technology has enhanced but not displaced this proud nerd army. Photography, GPS, and databases have vastly improved the data from birders, but nothing has replaced boots on the ground.

This month, a research project at the University of Adelaide reported a demonstration of a UAV mounted image system that, for once, beats human birders [1].

Specifically, the study compared the accuracy of humans versus a small survey quadcopter, on a task to count birds in a nesting colony.  In order to have a known ground truth, the tests used artificial colonies, populated by hundreds of simulated birds.  The repurposed decoys were laid out to mimic some actual nesting sites.

They dubbed it “#EpicDuckChallenge”, though it doesn’t seem especially “epic” to me.

The paper compares the accuracy of human counters on the ground, human counts from the aerial imagery, and computer analysis of the aerial imagery.

First of all, the results show a pretty high error for the human observers, even for the experienced ecologists in the study. Worse, the error is pretty scattered, which suggests that estimates of population change over time will be unreliable.

The study found that using aerial photos from the UAV is much, much more accurate than humans on the ground. The UAV imagery has the advantage of being overhead (rather than human eye level), and also holds still for analysis.

However, counting birds in an image is still tedious and error prone.  The study shows that machine learning can tie or beat humans counting from the same images.

Together, the combination of low-cost aerial images and effective image processing algorithms gave very accurate results, with low variability. This means that this technique would be ideal for monitoring populations over time, because repeated flyovers would be reliably counted.

This study has its limitations, of course.

For one thing, the specific task used is pretty much the best possible case for such an aerial census.  Unrealistically ideal, if you ask me.

Aside from the perfect observing conditions, the colony is easily visible (on an open, flat, uniform surface), and the ‘birds’ are completely static.  In addition, the population is uniform (only one species), and the targets are not camouflaged in any way.

How many real-world situations are this favorable?  (Imagine using a UAV in a forest, at night, or along a craggy cliff.)

To the degree that the situation is less than perfect, the results will suffer.  In many cases, the imagery will be poorer, and the objects to be counted less distinct and recognizable. Also, if there are multiple species, very active birds, or visual clutter such as shrubs, it will be harder to distinguish the individuals to be counted.

For that matter, I’m not sure how easy it will be to acquire training sets for the recognizer software.  This study had a very uniform nesting layout, so it was easy to get a representative subsample to train the algorithm.  But if the nests are sited less uniformly, and mixed with other species and visual noise, it may be difficult to train the algorithm, at least without much larger samples.

Still, this technique is certainly a good idea when it can be made to work.  UAVs are great “force multiplier” for ecologists, giving each scientist much greater range. Properly designed (by which I mean quiet) UAVs should be pretty unobtrusive, especially compared to human observers.

The same basic infrastructure can be used for many kinds of surface observations, not just bird colonies.  It seems likely that UAV surveying will be a common scientific technique in the next few decades.

The image analysis also has the advantage that it can be repeated and improved.  If the captured images are archived, then it will always be possible to go back with improved analytics and make new assessments from the samples.  In fact, image archives are becoming an important part of the scientific record, and a tool for replication, cross validation, and data reuse.

  1. Jarrod C. Hodgson, Rowan Mott, Shane M. Baylis, Trung T. Pham, Simon Wotherspoon, Adam D. Kilpatrick, Ramesh Raja Segaran, Ian Reid, Aleks Terauds, and Lian Pin Koh, Drones count wildlife more accurately and precisely than humans. Methods in Ecology and Evolution:n/a-n/a,
  2. University of Adelaide, #EpicDuckChallenge shows we can count on drones, in University of Adelaide – News. 2018.



Robot Blimp For Exploring Hidden Spaces

I noted earlier the discovery of what seems to be a chamber in the Great Pyramid at Giza. The discovery opens the question of how to further explore the hidden space without damaging the ancient structure.  One idea is to drill a small shaft, and push through a tiny robot explorer.

A research group at INRIA and Cairo University is developing a robotic blimp for such a mission.  The deflated blimp can be pushed through a 3cm shaft, then inflate and reconnoiter the hidden space.  The task requires a very compact and light system, and likely will operate autonomously.

Evan Ackerman interviewed senior investigator Jean-Baptiste Mouret for IEEE Spectrum [1].  He notes that a blimp is a good choice, because it is “pillowy”, and less likely to damage the structure.

Mouret describes the challenges imposed by the size and weight limits.  Conventional sensors, including GPS, would be too heavy and power hungry.  They are developing “bioinspired” sensors, based on bees and flies.  These include a miniature optic-flow sensor that can operate in low-light conditions.

Getting the robot into the space is one thing, making sure that it is retrieved is more difficult.  It is important not to litter the structure with a lost robot, so the robot will need to return to the tiny access hole, dock with the base, and fold up so it can be pulled out.  It will be designed with backup behaviors to search for the dock, even if damaged.

It will be years before any expedition to the Great Pyramid happens. The robot is still being developed and the measurements of the Pyramid are being refined.   The Pyramid is over 4,000 years old, so there is no need for haste.

  1. Evan Ackerman, Robotic Blimp Could Explore Hidden Chambers of Great Pyramid of Giza, in IEEE Spectrum – Automation. 2017.


Robot Wednesday

Sun2ice: Solar Powered UAV

One of the important use cases for UAVs is surveillance in all its forms. Small, cheap aircraft can cover a lot of area, carry a lot of different sensors, and swoop in to obtain very close up information.   In some cases, a human can directly control the aircraft (as in selfie cams and drone racing), but for many cases the UAV needs to be substantially autonomous.

Furthermore, remote observation generally needs long, slow flights, rather than short, fast ones. Range and flight duration are critical.

Remote sensing by UAVs is ideal for many kinds of environmental research, especially in remote areas such as deserts, oceans, or polar regions. A fleet of (inexpensive) UAVs can multiply the view of a single (very expensive) scientist by orders of magnitude, measuring a broad area, and identifying points of interest for detailed investigation.

This summer a group of researchers from ETH and the AtlantikSolar company have demonstrated a UAV that continuously monitored glaciers in Greenland. The Sun2ice is solar powered, so it charges its batteries as long as the sun is shining. In the polar summer, there is essentially 24 hour sunlight, so the UAV has power to fly continuously for months, at least in principle. Like other solar powered aircraft and boats, the AtlantikSolar needs not fuel and should be capable of extremely long missions.

Of course, flying over Greenland is difficult for any aircraft, and flying a small UAV continuously over remote and rugged glaciers is very challenging. The aircraft must deal with high winds and cold temperatures, even in good weather. With no pilot on board, the control systems must be highly automated.

The UAV must navigate over uninhabited territory, far from the humans back at base. It has to stay on station to collect data continuously, with little help from people. Magnetic compasses don’t work on Greenland, and continuous daylight means that celestial navigation is not possible either.

The researchers also had to deal with take off and landing from a remote field station. The video shows the UAV being delivered to its launch point via dogsled—Pleistocene technology deploying twenty first century technology. The test flights were successful, though flying time was less than a full day.

Flying an experimental solar-powered UAV as AtlantikSolar in Arctic conditions is very challenging due to the narrow sun angle, extreme climatic conditions, the weakness of the magnetic field used for the compass, and the absence of smooth grass-covered terrain to land a fragile airplane.

This technology is ideal for intense observation of glaciers and other natural phenomena. The UAV flies low enough to obtain high resolution images, and if it can stay on station, can provide updated data every hour or less. The UAV is cheaper than a satellite, and even than a piloted aircraft. It would be possible to deploy a fleet of UAVS to monitor a glacier or volcano in great detail for substantial periods.


  1. Philipp Oettershagen, Amir Melzer, Thomas Mantel, Konrad Rudin, Thomas Stastny, Bartosz Wawrzacz, Timo Hinzmann, Stefan Leutenegger, Kostas Alexis, and Roland Siegwart, Design of small hand-launched solar-powered UAVs: From concept study to a multi-day world endurance record flight. Journal of Field Robotics, 34 (7):1352-1377, 2017.


Robot Wednesday